The present invention relates to hydrogen production by reaction of aluminum metal with water, and more particularly, to a system and method of producing hydrogen gas by mechanical scraping of aluminum-containing surface in the presence of an aqueous medium.
Aluminum metal is known to react intensely with water. Production of hydrogen by means of the aluminum-water reaction is typically represented as:2Al+3H2O→Al2O3(s)+3H2(g)  (1)but may occur in more than one step, for example, according to the following two-step representation:2Al+6H2O→2Al(OH)3+3H2(g)  (2)2Al(OH)3→Al2O3(s)+3H2O  (3)
The reaction produces aluminum oxide on the surface of the aluminum, which substantially passivates the surface and reduces or entirely stops further reaction. Sundry efforts to achieve a sustained production rate of hydrogen have been made, and have been summarized in U.S. Pat. No. 6,506,360 to Andersen et al. These efforts include utilizing special aluminum-based alloys, introducing chemical additives, introducing catalytic materials, using a liquid or molten aluminum source, and applying a high power pulse of electrical current to initiate a reaction between an aluminum or aluminum alloy powder and water.
European Patent No. 0055134 B1 discloses a method for the production of hydrogen by inducing an electrical discharge between aluminum wire and an aluminum drum, both of which are immersed in water. When a voltage is applied between the wire and drum, an arching discharge takes place between them, inducing an electro-plasmic reaction. The reaction produces hydrogen and oxygen gas and aluminum oxide. The arcing between the wire and drum helps remove the oxide layer formed on the wire tip, exposing fresh aluminum to the water, whereby a continuous generation of hydrogen gas may be achieved.
Japanese Patent Document No. JP2001-31401A discloses a method for producing hydrogen gas, by a cutting processing or a grinding processing of aluminum or an aluminum alloy in water.
Various approaches to achieve a sustained production rate of hydrogen have been disclosed by U.S. patent application Publication No. 2007/0237994 to Nakai et al., and by U.S. Pat. Nos. 7,008,609, 7,200,954, and 7,235,226 to Watanabe et al.
The variety of these approaches, coupled with the exotic nature of many of these approaches, suggests there is a long-felt, unsatisfied need for improvements in methods and systems for producing hydrogen by reaction of aluminum metal with water.